A cellular radio mobile communication system appeared in the 1980s, and is used for meeting requirements for human voice communication at the beginning. On the basis of voice services, the cellular radio mobile communication system is gradually developed to meet requirements for the basic data communication of the human later. A conventional cellular radio communication system is deployed and operated by a radio network operator. Network construction is carefully planned by the operator. FIG. 1 is a schematic diagram of a network topology of a conventional cellular radio access network. As shown in FIG. 1, the siting of each macro base station (MNB, Macro (e) NB) is planned by the operator, and each macro base station may have several hundred meters or even several kilometers of radio coverage, thereby achieving nearly continuous seamless coverage within the operator's operation area.
With the advent of the mobile internet era, new demands for mobile applications, especially mobile applications requiring high-quality, high-speed, low-latency, boom. According to industry forecasts, on the one hand, radio mobile services will have thousands of times of growth in the next 10 years, and traditional radio communication systems that realize long-range macro coverage cannot meet such a huge capacity demand. On the other hand, according to the statistics of user communication behaviors and habits, it is found that most high-data-flow mobile services are concentrated in indoor environments and hot spots, such as shopping malls, schools, users' homes, large-scale shows and public venues, etc. However, indoor environments and hot spots are distributed widely and dispersedly, have small area and mass users. That is, the conventional cellular radio network having the characteristics of wide coverage, uniform coverage, and constant coverage cannot well adapt to the situation of centralized services in a small area. In addition, under the conventional cellular radio network, the cellular radio signal in the indoor environment is inferior to that in the outdoor environment due to various reasons, such as the blocking of a building and the like, resulting in failure of the conventional cellular radio network to meet the demand of future large data capacity in the indoor environment.
In order to solve the above problem, a small radio access network node (SRAN-node, abbreviated to a small node hereinafter) is proposed. Conceptually, the SRAN-node refers to a radio access network node that has a lower transmitting power and a smaller coverage area as compared with the conventional macro base station. Therefore, the SRAN-node may also be referred to as a low-power node (LPN), such as a Pico Node, a Femto/Home (e)NB, a relay, and any other possible access network apparatus having a transmitting power far lower than the conventional macro base station and capable of accessing the network through a radio communication link.
In order to meet huge capacity of future radio communication system, especially to meet a requirement of centralized large data volume in a certain area, those skilled in the art predict that the network capacity may be increased by increasing the deployment density of the SRAN-node in the certain area so as to meet user's requirements. Such a network densely deployed in the certain area is called as an Ultra Dense Network (UDN). FIG. 2 is a schematic diagram of deploying the UDN in a certain area of a conventional cellular radio access network. As shown in FIG. 2, each of a mansion 200, a stadium 210 and a hotspot 230 is deployed with a large number of SRAN-nodes.
The UDN can improve the network capacity. However, it is not expected to increase Capital Expenditure (CAPEX) and Operating Expense (OPEX) of the future network while increasing the network capacity. That is to say, the deployment of UDN needs to reduce man-made planning, optimization and management. The UDN should be deployed flexibly and rapidly in the indoor or outdoor hot areas or large traffic areas according to the network topology, network load, service requirements, and so on, and can be self-configured, self-optimized and self-healing. To achieve the above, those skilled in the art generally believes that only a part or a few of SRAN-nodes in the UDN can be accessed to a core network equipment through wired backhaul (such as optical fiber, cable, etc.); while other SRAN-nodes need to support radio backhaul. By taking advantage of the property of dense short-distance deployment among the SRAN-nodes, the interconnection and intercommunication among the SRAN-nodes are achieved through radio backhaul links among the SRAN-nodes, and the SRAN-nodes are accessed to the core network equipment through the radio backhaul link by passing the wireless connection (one hop) between two SRAN-nodes, or passing wireless connections (multiple hops) between multiple SRAN-nodes in turn. In this way, in the UDN network, communication data of a user equipment (UE) probably need to be transmitted over two or even more air interface transmissions. In the case that there are two air interfaces, the two air interfaces include an air interface radio access link (RAL) between the UE and the SRAN-node (denoted as SRAN-node-x) accessed by the UE and an air interface radio backhaul link between the SRAN-node-x and the SRAN-node having wired backhaul (denoted as SRAN-node-z). In the case that there are more than two air interfaces, taking three air interfaces as an example, the air interfaces include the RAL, an air interface radio backhaul link between the SRAN-node-x and an intermediate node (denoted as SRAN-node-y), and an air interface radio backhaul link between the SRAN-node-y and the SRAN-node-z.
In the future, a large number of SRAN-nodes will be densely deployed in the UDN, but only a few SRAN-nodes have a wired backhauls, causing the communication data of the UE likely to be transmitted through two or even more air interfaces. A technical problem required to be solved urgently is to ensure the security of such mobile communication system, so as to ensure the security the communication data of the UE when being transmitted through two or even more air interfaces. Currently, there is no specific technical method.